Due to the increasing energy demand, offshore oil and gas production is moving into deeper waters. For ensuring an efficient and secure production of hydrocarbons from a subsea well, processing facilities are being installed at the ocean floor. Such subsea installations can comprise a range of components, including pumps, compressors and the like as well as a power grid for providing such components with electric power. The power grid may for example comprise a subsea transformer, subsea switchgear and subsea variable speed drives (VSDs). Such components of a subsea installation may be installed at water depths of 3,000 meters or more, so that they are exposed to pressures up to or even in excess of 300 bars. To protect such components from the corrosive seawater and allow operation at these high pressures, they are provided with subsea enclosures.
The construction of such subsea enclosures is technically challenging. Furthermore, they need to go through a qualification procedure in order to ensure that they are suitable for their intended purpose. This is a time- and cost-intensive process. Pressure compensated enclosures are known in which the internal pressure is equalized or balanced to the pressure prevailing in the ambient seawater. A pressure compensator may be used for such purpose. Such enclosures are generally filled with a dielectric liquid, in order to keep volume changes due to the increase in pressure and due to temperature changes relatively low. The dielectric liquid can further support the cooling of electric and electronic components disposed therein.
For operating subsea equipment such as subsea pumps and compressors, it is desirable to make use of a subsea frequency converter which can provide AC electric power at variable frequency. Such device can be used to drive AC motors at variable speed and can thus be termed variable speed drive (VSD). Speed control of AC electric motors comprised in such subsea equipment thus becomes possible. Different types of equipment and different installation sites might require variable speed drives having different power ratings, different control ranges or different requirements regarding the quality of the output AC electric power. When providing subsea variable speed drives for such different requirements, new subsea enclosures are required. Changing the configuration of a variable speed drive is thus a time- and cost-intensive procedure and furthermore requires significant development efforts.
The document US 2013/0286546 A1 discloses a subsea electrical distribution system having a modular subsea circuit breaker. By providing plural circuit breaker modules, a redundancy of the circuit breakers is achieved.
The document EP 2533619 discloses an energy conversion device having a housing with a main section and an end section. The main section can be slid away from the end section along the longitudinal direction without requiring the disconnection of the electrical connections, thus facilitating the maintenance of the conversion device.